JDBC获取新增记录的自增主键
 
常常在使用Hibernate、iBatis时候,当插入一条数据的时候,实体Bean的原空主键就赋上新值了。
在JDBC中,也可以通过变相的手法来做到这点。下面是个测试的小例子。
 
一、环境
 
MySQL5.1
mysql-connector-java-5.1.10
jdk1.5
 
 
CREATE TABLE book(
    code bigint(20) unsigned NOT NULL AUTO_INCREMENT,
    kind varchar(45) NOT NULL,
    name varchar(45) NOT NULL,
    PRIMARY KEY(code, kind)
) ENGINE = InnoDB AUTO_INCREMENT = 1 DEFAULT CHARSET = latin1
 
二、获取自增主键
 
注意:使用prepareStatement(String sql, int autoGeneratedKeys) 来定义PreparedStatement对象。并且指定:Statement.RETURN_GENERATED_KEYS
 
import lavasoft.common.DBToolkit;

import java.sql.*;

/**
* JDBC获取新增记录的主键
*
* @author leizhimin 2009-12-4 13:20:15
*/

public class InsertKeyTest {

        public static void main(String[] args) {
                insertWithStaticSQL();
                insertWithParperedSQL();
        }

        /**
         * 预定义SQL模式,获取新增记录的主键
         */

        public static void insertWithParperedSQL() {
                Connection conn = null;
                try {
                        conn = DBToolkit.getConnection();
                        String sql = "insert into testdb.user (name, pswd) values(?,?)";
                        PreparedStatement pstmt = conn.prepareStatement(sql, Statement.RETURN_GENERATED_KEYS);
                        pstmt.setString(1, "laozhang");
                        pstmt.setString(2, "111111");
                        pstmt.executeUpdate();
                        //检索由于执行此 Statement 对象而创建的所有自动生成的键
                        ResultSet rs = pstmt.getGeneratedKeys();
                        if (rs.next()) {
                                //知其仅有一列,故获取第一列
                                Long id = rs.getLong(1);
                                System.out.println("-----预定义SQL模式-----id = " + id);
                        }
                } catch (SQLException e) {
                        e.printStackTrace();
                } finally {
                        DBToolkit.closeConnection(conn);
                }
        }

        /**
         * 静态SQL模式,获取新增记录的主键
         */

        public static void insertWithStaticSQL() {
                Connection conn = null;
                try {
                        conn = DBToolkit.getConnection();
                        String sql = "insert into testdb.user (name, pswd) values('ttttt','121')";
                        PreparedStatement pstmt = conn.prepareStatement(sql, Statement.RETURN_GENERATED_KEYS);
                        pstmt.executeUpdate();
                        //检索由于执行此 Statement 对象而创建的所有自动生成的键
                        ResultSet rs = pstmt.getGeneratedKeys();
                        if (rs.next()) {
                                //知其仅有一列,故获取第一列
                                Long id = rs.getLong(1);
                                System.out.println("-----静态SQL模式-----id = " + id);
                        }
                } catch (SQLException e) {
                        e.printStackTrace();
                } finally {
                        DBToolkit.closeConnection(conn);
                }
        }
}
 
执行结果:
-----静态SQL模式-----id = 8
-----预定义SQL模式-----id = 9

Process finished with exit code 0